1. Field
The embodiment relates to a light emitting device, a method of fabricating the light emitting device, a light emitting device package, and a lighting system.
2. Background
A light emitting device includes a P-N junction diode having a characteristic of converting electrical energy into light energy. The light emitting device may include compound semiconductors belonging to group III and V on the periodic table. The light emitting device can represent various colors by adjusting the compositional ratio of the compound semiconductors.
When forward voltage is applied to the LED, electrons of an N layer are combined with holes of a P layer, so that energy corresponding to an energy gap between a conduction band and a valance band may be generated. The energy is mainly emitted in the form of heat or light. In the case of the LED, the energy is generated in the form of light.
For example, a nitride semiconductor represents superior thermal stability and wide bandgap energy so that the nitride semiconductor has been spotlighted in the field of optical devices and high-power electronic devices. In particular, blue, green, and UV light emitting devices employing the nitride semiconductor have already been commercialized and extensively used.
Among light emitting diodes having a visible ray region, a light emitting diode (red LED) having a wavelength representing high utilization is a red element, which represents a superior visibility in the same brightness as compared with green and yellow elements. Accordingly, the red element has been extensively used for various fields such as traffic lights, stop lamps of vehicles, and various displays.
Meanwhile, in the case of a red LED according to the related art, since low power is required, low current is applied, so that magnesium (Mg) diffusion issues may not be important. However, recently, as the demand for a high-power red LED chip is increased, high current is applied, so that the Mg diffusion issue into the active region has been spotlighted, and Mg existing in a GaP window layer is diffused in an active region when a reliability test is performed, so that light output power drip (Po drop) may occur.